Avi Kivity wrote:
> Alexander Graf wrote:
[snip]
>>>> static int kvm_resume(struct sys_device *dev)
>>>> {
>>>> - hardware_enable(NULL);
>>>> + if (atomic_read(&kvm_usage_count))
>>>> + hardware_enable(NULL);
>>>> return 0;
>>>> }
>>>>
>>> Move the test to hardware_enable()? It's repeated too often.
>>>
>>
>> What do we do about the on_each_cpu(hardware_enable) cases? We couldn't
>> tell when to activate/deactive virtualization then, as that's
>> semantically bound to "amount of VMs".
>>
>
> I don't understand. Moving the test to within the IPI shouldn't
> affect anything.
>
Actually it's there already. Since we have the cpu_isset if here, we
won't get disabling when it's disabled or enabling when it's enabled on
a per-cpu basis. That code would've just saved us the IPIs :-).
So I'll add hardware_{en,dis}able_all functions that do the locking and
increase / decrease the counter. Disable is used twice, while enable
only once. But for the sake of code readability, I think it might be a
good idea to have both of them be functions.
Also the locking isn't really needed in most cases (CPU hotplug,
suspend, resume, reboot, exit), since we don't schedule there.
Alex
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